From: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
To: Eric Dumazet <eric.dumazet@gmail.com>, Willy Tarreau <w@1wt.eu>
Cc: netdev@vger.kernel.org,
Maggie Mae Roxas <maggie.mae.roxas@gmail.com>,
Thomas Petazzoni <thomas.petazzoni@free-electrons.com>,
Gregory CLEMENT <gregory.clement@free-electrons.com>
Subject: Re: [PATCH] net: mvneta: fix Tx interrupt delay
Date: Tue, 02 Dec 2014 14:12:10 -0300 [thread overview]
Message-ID: <547DF2EA.2020908@free-electrons.com> (raw)
In-Reply-To: <1417522688.5303.35.camel@edumazet-glaptop2.roam.corp.google.com>
Eric,
On 12/02/2014 09:18 AM, Eric Dumazet wrote:
[..]
>
> I am surprised TCP even worked correctly with this problem.
>
> I highly suggest BQL for this driver, now this issue is fixed.
>
Implementing BQL for the mvneta driver was something I wanted to do a
while ago, but you explained that these kind drivers (i.e. those with
software TSO) didn't need BQL, because the latency that resulted from
the ring was too small.
Quoting (http://www.spinics.net/lists/netdev/msg284439.html):
""
Note that a full size TSO packet (44 or 45 MSS) requires about 88 or 90
descriptors.
So I do not think BQL is really needed, because a 512 slots TX ring wont
add a big latency : About 5 ms max.
BQL is generally nice for NIC supporting hardware TSO, where a 64KB TSO
packet consumes 3 or 4 descriptors.
Also note that TCP Small Queues should limit TX ring occupancy of a
single bulk flow anyway.
""
Maybe I misunderstood something?
--
Ezequiel García, Free Electrons
Embedded Linux, Kernel and Android Engineering
http://free-electrons.com
next prev parent reply other threads:[~2014-12-02 17:14 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-12-02 7:13 [PATCH] net: mvneta: fix Tx interrupt delay Willy Tarreau
2014-12-02 12:18 ` Eric Dumazet
2014-12-02 12:30 ` [PATCH] net: mvneta: fix race condition in mvneta_tx() Eric Dumazet
2014-12-02 12:37 ` Eric Dumazet
2014-12-02 12:40 ` Willy Tarreau
2014-12-09 1:55 ` David Miller
2014-12-02 12:39 ` [PATCH] net: mvneta: fix Tx interrupt delay Willy Tarreau
2014-12-02 13:04 ` Eric Dumazet
2014-12-02 13:24 ` Willy Tarreau
2014-12-02 15:17 ` Eric Dumazet
2014-12-02 17:12 ` Ezequiel Garcia [this message]
2014-12-02 17:31 ` Dave Taht
2014-12-02 18:39 ` Eric Dumazet
2014-12-09 1:44 ` David Miller
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